Java enum with string values

In this guide to Java enum with string values, learn to create enum using strings, iterate over all enum values, get enum value and to perform reverse lookup to find enum by string parameter.

1. Create java enum with string values

Java program to create enum with strings. This enum contains deployment environments and their respective URLs. URLs are passed to enum constrctor for each enum constant.

public enum Environment 
{
	PROD("https://prod.domain.com:1088/"), 
	SIT("https://sit.domain.com:2019/"), 
	CIT("https://cit.domain.com:8080/"), 
	DEV("https://dev.domain.com:21323/");

	private String url;

	Environment(String envUrl) {
		this.url = envUrl;
	}

	public String getUrl() {
		return url;
	}
}

2. Iterate enum constants

To iterate over enum list, use values() method on enum type which return all enum constants in an array.

//Get all enums
for(Environment env : Environment.values())
{
	System.out.println(env.name() + " :: "+ env.getUrl());
}

Output:

PROD :: https://prod.domain.com:1088/
SIT :: https://sit.domain.com:2019/
CIT :: https://cit.domain.com:8080/
DEV :: https://dev.domain.com:21323/

3. Java enum to String

To get single enum value (e.g. get prod URL from enum constant) use it’s value method, you created.

//Using enum constant reference
String prodUrl = Environment.PROD.getUrl();

System.out.println(prodUrl);

Output:

https://prod.domain.com:1088/

4. Get enum by name – enum string parameter

If you want to get enum constant using it’s name, then use valueOf() method.

//First get enum constant reference from string
Environment sitUrl = Environment.valueOf("SIT");

System.out.println(sitUrl.getUrl());

Output:

https://sit.domain.com:2019/

5. Reverse Lookup – Get enum name from value

Many times, we will have the value of enum with us, and we will need to get enum name by string value. This is achieved using reverse lookup.

In reverse lookup, enum internally maintains a map of value-enum as key-value pair. This map is searched, application need to find enum with it’s associated string value.

import java.util.HashMap;
import java.util.Map;

public enum Environment 
{
	PROD("https://prod.domain.com:1088/"), 
	SIT("https://sit.domain.com:2019/"), 
	CIT("https://cit.domain.com:8080/"), 
	DEV("https://dev.domain.com:21323/");

	private String url;

	Environment(String envUrl) {
		this.url = envUrl;
	}

	public String getUrl() {
		return url;
	}
	
	//****** Reverse Lookup Implementation************//

	//Lookup table
	private static final Map<String, Environment> lookup = new HashMap<>();
 
	//Populate the lookup table on loading time
	static 
	{
		for(Environment env : Environment.values())
		{
			lookup.put(env.getUrl(), env);
		}
	}
 
	//This method can be used for reverse lookup purpose
	public static Environment get(String url) 
	{
		return lookup.get(url);
	}
}

To use this reverse lookup, in application code use enum.get() method.

//Get enum constant by string - Reverse Lookup
String url = "https://sit.domain.com:2019/";

Environment env = Environment.get(url);

System.out.println(env);

Output:

SIT

Read More: Complete Java Enum Guide

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Happy Learning !!

Read More:

Java Enum Tutorial